U.S. gross domestic product (GDP) is considered one of the United States’ most vital economic statistics. Each release of GDP by the U.S. Bureau of Economic Analysis (BEA) can have a significant impact on decisions made by government officials, businesses, investors, and American households. A number that important must have the full faith and confidence of the public behind it. No one wants to chart his or her economic future on data whose accuracy or objectivity is in question.

So how do we keep the numbers secure? Each month, as the final source data come together, BEA implements “GDP lock-up.” The lock-up is governed by a set of rigorous procedures to ensure the security of GDP and other sensitive statistics.

As the numbers begin to come together, the staff of BEA’s National Economic Accounts Directorate has Internet access disabled and implements other measures to further restrict access to portions of the building where this staff works and the data are kept. Data are kept compartmentalized so that only a few key staff members have access to enough pieces to assemble the estimate. Key staff, including members of BEA’s executive staff and others whose expertise is necessary for the final review, turn their focus to the final estimation. As always, these staff members are forbidden from speaking to any non-BEA staff about the estimates.

On the eve of the public release of the GDP report, BEA’s leaders and other designated staff enter a specially designed suite of rooms to review the final numbers. All telephone and Internet connections in the room are disabled. Cell phones and Blackberrys must be checked in and locked away, and thick curtains are pulled over the few windows. While in lock-up, certain rules and customs are always followed. For example, the final GDP estimate is never said out loud. Additionally, given that lock-ups usually take at least 5 to 6 hours to complete, someone is assigned the critical task of bringing in snacks to munch on.

The review process is comprehensive, with a systematic review of each component of the estimate presented and approved by the Bureau’s leaders. Once the estimate is finalized, the staff proceeds to draw up all the necessary documents and files related to the GDP and personal income releases. These include the news releases, graphs, and technical notes you see published. Copies of the final documents are made on secure equipment and are locked away in a specific room until time for their release.

The participants are not allowed to leave the room until they are officially dismissed by the Bureau’s Director. At the earliest, that’s around 6 p.m., following the closure of U.S. financial markets, although some lock-ups have been known to stretch late into the night. Once the lock-up ends and employees have signed out, they are forbidden to talk about the estimates with anyone until the numbers are officially released at 8:30 a.m. the next morning. Any notes or doodles jotted down during the lock-up or ink cartridges and scrap paper used during the process must be turned in to the lock-up manager. Those materials remain secure until the GDP numbers are made public the following morning. For the next 12 hours or so, the only people who know the new estimate of U.S. GDP are a select few BEA staffers and the Chairman of the President’s Council of Economic Advisors, who by law, is the only non-BEA person provided an advance copy.

The final steps in this embargo process ensure that the data is provided to everyone at the same, precise time. At 7:30 a.m., a representative from BEA delivers the GDP news release to members of the media in another specially designed facility at the main building of the U.S. Department of Commerce. In the media lock-up room, accredited members of the news media have designated work stations, with controlled access to the Internet. There is another set of lock-up rules that govern the media’s pre-release access to the data. All reporters must sign in and lock their cell phones in a special case that blocks their signals. The media room is locked promptly at 7:30 a.m., with no one allowed to exit after that. Reporters are cut off from all communications at that time. They have 60 minutes to write their stories. At precisely 8:30 a.m., Internet access to their workstations is restored so they can post their stories to the public.

Meanwhile, back at BEA, the final GDP release files are delivered at 7:45 a.m. to the Bureau’s Web team, who gather in another specially designed and outfitted room, where communications have also been cut off. The Web team systematically codes and processes each of the specially designated files on two computers simultaneously, to ensure redundancy. Then at the strike of 8:30 on an official atomic clock, the team uploads the files to the Web and thus to the outside world.

Similar procedures are used to ensure the security and integrity of all of BEA’s releases.